Process for the pyrolytic decomposition of hydrocarbons



M. B. COOKE July 7, 1936.

` PROCESS Foa THE PYROLYTIG DEcoMPosITIoN oF HYDROCARBONS Filed March l2, 1932 QM. NAM NQQU IN VEN TOR. Mayr/e 15. Coo/fe By.

A TT ORNE Y.

Patented July 7, 1936 PATENT OFFICE PROCESS FOR THE PYBOLYTIO BECOM- POSITION F HYDB'OCABBDNS Maurice B. Cooke, New York, N. Y. Application March 12, 1932, Serial No. 598,504

1 Claim. (Cl. 196-67) My invention relates to a process for the pyrolytic decomposition of hydrocarbon oils to form gasoline-like hydrocarbons suitable for using as a motor fuel having high antiknock qualities.

'6 The process is usually known as a cracking process and relates more particularly to the cracking of hydrocarbons in the vapor phase by hot gases of combustion.

When fuel is burned with no excess of air, the

temperature of combustion is between 3,000 and l4,000 F. These temperatures are too high for eiiicient cracking and accordingly they must be tempered or brought down to about 1,500 F. in Order to give an ecient cracking process.

In an application 'onf William O. Keeling, Serial No. 586,573, now U.S. Patent 1,991,750, a. method of tempering the combustion gases by means of a cooler, inert gas is disclosed.

This application relates to an improvement in 2o my co-pending application, Serial No. 598,502, led March 12, 1932, now Patent No. 2,016,798, issued October 8, 1935 to Maurice B. Cooke.-

When a great volume of gas is introduced into the fractionating tower, many disadvantages result. The' equipment must be made a larger size.

l The volume of gas to be compressed for absorption purposes is so increased that the process becomes expensive. The use of a cool. inert gas to temper the combustion gases represents a direct loss of heat besides increasing the volume of the gases to be handled.

One object of my invention is to avoid the disadvantages above pointed out. with special reference to reducing the volume of the gas to be handled in the fractionatlng equipment.

It will be noted that the instant invention differs from my above mentioned co-pending application in .that I use steam to give anadditional heat carrier and to temper the hot products of combustion, so that the separation of the water in the pre-fractionation condensing stage will enable the use of a smaller main fractionating tower.

Another object of my invention is to partially temper the hot products of combustion by steam.

A further object of my invention is to provide a process in which fractionating equipment of small dimensions may be used due to the fact that no considerable amount of flue gas or iixed gas pass through the fractionating zone.

Another object 'of my invention is to provide a process in which the hot gases of combustion are tempered by means of heat exchange.

A further object of my invention is to employ the gas heat for topping the charging stock, va-

porizing the charging stock for conversion into the vapor phase and supplying heat for other purposes such as distilling or the generation or high superheating of steam.

Still another object of my invention is to pro- 5 vide a vapor phase cracking process in which hot gases of combustion are used to supply the cracking heat which is flexible of control and eflicient in operation.

Still another object of my invention is to check 10 the reaction to prevent over-cracking by means of shock chilling the products of reaction.

Other objects of my invention will appear from the following description:

The iigure shows a diagrammatic View of one 15 embodiment of the process of my invention.

In general, my invention consists in burning fuel and air with surface combustion in a furnace to supply hot gases of combustion substantially devoid of free oxygen. I charge crude oilfrom 20 storage through suitable heat exchangers into an accumulator tank. Oil is pumped Vfrom the accumulator tank through a coil situated in my furnace' where the heat necessary to convert a substantial portion of the charging stock into 25 vapors is-supplied. The temperature of the hot gases of combustion will be lowered and lose part of their heat in heating the oil in the coil and thus be tempered by indirect heat exchange. The heated charging stock is passed into a flash 30 evaporator whence the vapors are withdrawn and passed to the cracking zone. In the cracking zone the vaporized hydrocarbons encounter the hot gases of combustion which have been tempered to about 1,500 F. The hot gases of com- V35 bustion admixing with the vapors bring the mixture to about 1,050 F. at which temperature cracking takes place rapidly. The increase in volume is accommodated for by a progressively increasing cross sectional area. After leaving the 40 cracking zone, the products of the reaction are shock chilled by means of an oil spray. The products, after being chilled. pass into a tar separator. The tar laden quenching oil is drawn through a cooler and pumped to storage and may be used 45 for fuel oil. The vapors and gases are passed through a sectional entrainment condenser through suitable heat exchangers and into a separator, whence the uncondensed gases are withdrawn overhead and allowed to pass into 5o the gas main. It will be noted that this is the novel step in which the excess and uncondensed gases are withdrawn from the system in order to prevent their being passed through the fractionating tower. The water is withdrawn from 55 the bottom of the separator. 'I'he condensate is then pumped from the separator through suitable heat exchangers through a second coil in my furnace where the condensate will be revaporized. The revaporized products are passed lnto the fractionating tower.

The condensate formed in the entrainment condenser collects in suitable pockets and may be passed either into the separator or into a frac--l tionating tower depending upon their nature and character.

The reflux condensatefrom the fractionating tower is withdrawn and pumped through a cooler in order to reduce the temperature thereof to render it suitable as a quenching medium. After passing through the cooler, itis passed through the sprays in order to be used in the chilling zone. A portion of the reux condensate from the fractionating tower may be diverted into the accumulator for recycling. The vapors withdrawn from the fractionating tower are cooled ,and passed into a separator from which the water is withdrawn. The condensate is withdrawn las gasoline and passed to storage.

More particularly, referring now to the drawings, gas from the gas main I is taken through branch line 2, through compressor 3, Vinto gas supply tank 4, from which it passes through line 5, valve 6, into the mixing chamber 1 of the surface combustion burner. Compressed air entering through line 8 passes through valve 9 into the mixing chamber 1, where the mixture thus formed will burn with surface combustion on the granules of refractory material I 0 to form hot gases of combustion in the combustion chamber II. Hydrocarbon oil to be processed enters through line I2, passes through valve I3 and is pumped by pump I4 through line I5, through heat exchanger I6, through line I1, to the accumulator I8. The oil thus preheated leaves the accumulator I8 through line I9 and is pumped by pump 20 through valve 2|, through line 2:2, into the heating coil 23. The incoming charge passing through heatingcoil 23 will temper the hot products of combustion entering the furnace 24. In so doing, the charge will be itself heated to a vaporizing temperature. The oil leaves the heat-k ing coil 23 through line 25 and passes into the fiash evaporator 26 in which the heated oil is flashed into vapors. 'I'he unvaporized portion is withdrawn from the bottom of the flash evaporator through the line 21, through valve 28, through heat exchanger 29, through cooler 38,

and is pumped by pump 3| to storage through line 32 for use as a fuel oil. The vaporized oil leaves the ash evaporator through line 33 and valve 33 and passes into the mixing zone 34 in which the hydrocarbon vapors are commingled with the hot products of combustion coming from the furnace 24. After being admixed the reaction will take place in the cracking zone 35 in which the hydrocarbon vapors are pyrolytically decomposed to form hydrocarbons having a lower molecular weight and suitable for use as a motor fuel. AV

chamber of progressively increasing volume is provided to permit the'expansion to take place without building up `back pressure. After the reaction has progressed for a sufficient interval of time, inasmuch as the reaction at the temperature of 1,050 F. Vwill take place very rapidly, I provide oil sprays 36, 31 and 38 for quenching the hot products to check the reaction in order to prevent overcracking. 'Ihe hot gases of combustion, it will be remembered, are generated at a temperature between 3,000 F. and 4,000 F.

After tempering the hot products of combustion will have a temperature of about 1,500 F. When the oil vapors from the ash evaporator are admixed with the hot gas of combustion at a temperature of 1,500 F., the resultant mixture will 5 have a temperature of about 1,050"v F., at which the cracking takes place.

After the reaction has been checked by quenching, the products pass into the separator 39. The heavy, tarry residue which forms in the separator 10 is withdrawn from the bottom thereof through line 40 and is passed. through heat exchanger 29, cooler 30, to fuel oil storage, together with the vaporized oil from the ash evaporator coming A through line 21. 15

The vapors and gases which will be largely vapors containing the products of reaction, gases and steam, are withdrawn from the separator through line 4I and passed into the sectional entrainment condenser. The temperature of the 20 vapors entering the sectional entrainment con- -denser will be in the neighborhood of 750 F.

I pump clean water through valve controlled line 42 by pump 43, through line 44, through heat exchanger 45, into line 46, whence the incoming 25 Water will pass through the tubes 41 of the sectional entrainment condenser 48. It is to be noted that the incoming water will pass in counterflow relation to cool the vapors entering the sectional entrainment condenser through line 4I. The 30 water will be converted into steam which leaves the tubes 41 and passes into line 49 into the steam supply tank 50 which is suitably lagged to prevent heat radiation, as is all other equipment in which high temperatures exist.

Steam from the steam supply tank passes through line 5I through valve 52 and is allowed to enter the zone above the point of complete combustion of the surface combustion burner, at 53. It will be noted that the steam admixing with the hot combustion gases from the surface combustion burner at 53 will partially reduce the temperature of the hot combustion gases to bring them nearer the temperature at which the reaction takes place. The steam thus supplied will furnish an additional heat carrier medium, and has the advantage of being condensable enabling the reduction of the quantity of fixed gas which must pass through the fractionating tower. This 50 will enable me to use a smaller main fractionating tower than has heretofore been used in the processes of my copending applications Serial No. 585,488, filed January 8, 1932, and Serial No. 598,502, filed March I2, 1932, now U. S. Patent 2,016,798.

The condensate formed in the sectional Aentrainment condenser will collect in pockets 54', 55' and 56', whence it may be passed in whole or in part into the separator or fractionating-tower through 60 lines 51' and 58' respectively, by the agency of valves 59', 60', 6I and 62'. The products are then Withdrawn from the sectional entrainment condenser through line 63'and pass through heat exchanger 45, heat exchanger 46 and cooler 41 65 into the separator 48. The incoming fresh water to be converted into steam is the cooling medium burner, is condensed in the bottom of the separator 48' from which it is drawn oi through line 'I'he condensed products are pumped through line 52 by pump 53', through heat exchanger 46', and into line 54, which terminates in a manifold. A portion of the condensate may be diverted through valve controlled line 55 into line 22 for recycling. The condensate normally passes through valve controlled line 56 through heat exchanger 51, into line 58, line 59, through heat exchanger 29, into line 60, whence it passes to a second coil 6| situated in the furnace 24. A portion of condensate passing through heat exchanger 51 may be diverted through line 62 and passed into line 22 for recycling. The heat exchanger 51 may be by-passed, if desired, by valve controlled line 63. The condensate in passing.

through coil 6I, will temper in part the products of combustion, and will itself be revaporized.

The vapors leave the coil 6| through line 64 and pass into the fractionating tower 65.

Steam may be drawn from the supply tank 50 through line 66 and injected into the fractionating tower through valve 61, for stripping the heavy fractions of the lighter vapors. 'Ihe reux condensate in the fractionating tower is withdrawn through line 68 and passed through line 69, through heat exchanger 51, andpumped by pump 10 through cooler 1I, through line 12 and valve controlled branch lines 13, 14 and 15 for delivery to quenching sprays 36, 31 and 38 respectively. A portion ofthe reux condensate of the fractionating tower may be diverted through valve controlled line 16 and passed into the accumulator I8 for recycling.

The vapors from the fractionating tower pass through line 82, through heat exchanger I6,

through cooler 83, through line 84 into separator 85. A portion of the steam will be condensed in cooler 83 and will form water in the bottom of the separator 85. This water is withdrawn through line 86. The gasoline-like hydrocarbons are withdrawn through line 81 and passed to storage.

It will be appreciated that my process has many advantages. I temper the hot products of combustion by means of heat exchange and use the heat obtained by tempering to perform useful steps in my process. The thermal vefiiciency of my process will be exceedingly high. The ilexibility of control is manifest. The temperature' of the combustion gases, the temperature of the quenching oil and hence the temperature of reaction may be controlled within close limits. I am enabled, by my process, to crack hydrocarbon oil in the vapor phase and obtain a gasoline-like hydrocarbon suitable for use as a motor fuel and having an exceedingly high antiknock value. I may use a portion of the gas formed in my process for other purposes where gaseous fuel may be needed. It will be noted that the cracking reaction takes place in the pure vapor phase, it being impossible for any hydrocarbon oil which is not in the vapor form to be present. This insures the absence of the danger ot the formation of coke or carbon deposits within my cracking zone. It will be understood, of course, that suitable lagging is provided throughout the piping and the piece of apparatus used in my process to prevent the loss of heat by radiation. By withdrawing a large quantity of the gas from the system before fractionating the products of combustion, and tempering by steam I am enabled to avoid large fractionating equipment and to dispense with the necessity of treating a disproportionate amount of gas in my gasoline absorption treatment It will be understood that certain features and sub-combinations and operations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claim. It is further obvious that various changes may be made in details within the scope of my claim without departing from the spirit of my invention. It is, thereforato be understood that my invention is not to be limited to the specic details shown and described.

By this method of cracking hydrocarbons in the Y vapor phase, in which the hydrocarbons are combined with the combustion gases, the latter being maintained at selected, controlled, temperatures of reaction, a motor fuel having a high octane number and high antiknock value is obtained. The process eliminates parasitic cracking which accompanies conventional cracking methods, in which the hydrocarbons are converted in tubular containers and heated by external circulation of the combustion gases thereabout. The intimate mixture of the combustion gases with the hydrocarbon vapor produces a distribution of heat impossible with the conventional tubular cracking processes.

Having thus described my invention, what I claim is:

A process for converting hydrocarbon oils into lower boiling hydrocarbons including the steps of generating hot gases of combustion, heating a hydrocarbon oil to vaporizing temperatures by passing the same in an elongated conned stream in heat exchange relation with the hot gases of combustion, controlling the temperature of the hot gases by mixing steam therewith, separating the heated oil into vapors and unvaporized oil and admixing the vapors with hot gases of combustion which have been tempered by heating the oil and by mixing steam therewith, allowing a time interval of reaction and then arresting the reaction by spraying cool oil in contact with the reacting mixture, condensing the products of reaction, separating the condensate from the uncondensed gases, revaporizing the condensate by passing the condensate in an elongated conned stream in heat exchange with the hot gases to supply the heat of vaporization and to further temper the hot gases of combustion and fractionating the vapors to recover lower boiling 

